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In the same lightning flash, whose usual duration is less than a second, there can be multiple negative cloud-to-ground strokes with different terminations or following a preexisting channel to the ground. In contrast, it is not common to have multiple positive cloud-to-ground (+CG) strokes, and especially multi-stroke +CG flashes sharing the same channel to ground are very rarely observed. This polarity asymmetry is not well understood and many aspects are debated. In this letter, we present for the first time a very high frequency (VHF) radio band observation of a multi-stroke +CG flash along the same channel, observed simultaneously by a VHF broadband interferometer and a Lightning Mapping Array in north-central Colombia. These combined observations have unprecedented temporal and spatial resolution and allowed us to observe in detail the development of the flash and especially to understand the initiation mechanism of the subsequent positive stroke.

Gigantic jets are electric discharges that on rare occasions can be seen at night shooting out of the top of tropical thunderclouds, reaching the ionosphere (90 km). Using sensitive camera systems and detection software, we recorded 70 events over northern Colombia and adjacent seas, most of them captured between 2016 and 2022. This is the first study to compare the meteorological background conditions for thunderstorms that produced gigantic jets in 48 nights against 83 reference cases with monitored thunderstorms that did not produce jets, using vertical profiles from ERA5 reanalysis near the event location. From the vertical profiles, various meteorological parameters are calculated, grouped by metrics of the low level convective parcel, instability, humidity, warm cloud and mixed phase parameters, and vertical wind shear, not limited to default levels. We report statistically significant differences and effect sizes (Cohen's d) for gigantic jet producing environments compared to null environments. Gigantic jets are produced in conditions with reduced low level temperatures in combination with warmer mid levels. This causes a lower cloud base and higher -10 °C isotherm altitude, thus a greater warm cloud depth, as well as reduced updraft and downdraft buoyancy. Over northern Colombia the non-GJ producing storms tend to grow in an environment that supports more vigorous, multicellular convection by enhanced low-level storm-relative winds and stronger downdrafts. Over western Colombia, the non-GJ cases tend to have a lower equilibrium level while having favorable warm cloud parameters. No evidence is found for hypotheses that upper level vertical wind shear enables gigantic jet production, nor are overshooting tops larger. The findings can be used for forecasting gigantic jets and their climatologically optimal regions on Earth. We speculate that the environmental conditions shift the droplet size distribution towards larger drops at the cost of cloud droplets, with enhanced droplet shattering ice multiplication processes as they freeze. Depending on convective evolution, low rime accretion rates could briefly expand the negative charge region downward by inverse polarity charging while the upper positive charge concentration may weaken at the same time, which could lead to a temporary negatively imbalanced electric potential distribution in the cloud needed for gigantic jet emission.

La tempesta Glòria va ser una borrasca extra-tropical que es va intensificar durant diversos dies sobre el mar Mediterrani occidental, aportant pluges i nevades intenses, vents forts i valors record de l'onatge en àrees de al sud d'Europa i nord d'Àfrica. Aquest treball de fi de grau busca avaluar de manera quantitativa els efectes de la tempesta sobre el litoral de la Mediterrània occidental. Es desenvolupen uns índexs numèrics on s'analitzen valoracions físiques, mediambientals i socials per a l'avaluació de l'impacte del temporal. La tormenta Gloria fue una borrasca extra-tropical que se intensificó durante varios días sobre el Mar Mediterráneo occidental, aportando lluvias y nevadas intensas, vientos fuertes y valores record del oleaje en áreas del sur de Europa y norte de África. Este trabajo de fin de grado busca evaluar de manera cuantitativa los efectos de la tormenta sobre el litoral del mediterráneo occidental. Se desarrolan unos índices numéricos donde se analizan valoraciones físicas, mediambientales y sociales para la evaluación del impacto del temporal. Storm Gloria was an extra-tropical storm that intensified over several days over the western Mediterranean Sea, bringing heavy rain and snow, strong winds and record wave values ​​in areas of southern Europe and North Africa. This end-of-degree project seeks to quantitatively evaluate the effects of the storm on the western Mediterranean coast. Numerical indexes are developed where physical, environmental and social evaluations are analyzed for the evaluation of the impact of the storm.

El 20 de enero de 2020, el temporal Gloria provoca el fallo del tramo final de la pasarela que lo unía a la plataforma del pantalán del Pont del Petroli con la playa de Badalona (España). La presente tesis se centra en la recopilación y análisis de datos relacionados con la acción de olas extremas y cargas experimentales relacionadas. Las pruebas de modelos físicos a escala 1:10 se llevaron a cabo en la instalación de canal CIEM de la Universitat Politècnica de Catalunya. Se ha evaluado hasta qué punto estos resultados experimentales concuerdan con las formulaciones existentes propuestas en la literatura. Finalmente, se ha realizado una comparación visual entre el modelado experimental y la poca información de los impactos observados durante la tormenta Gloria. On January 20, 2020, the storm Gloria causes the collapse of the final part of the walkway that connected it to the extremal platform of the Pont del Petroli pier to the beach of Badalona (Spain). The present thesis focuses on the collection and analysis of data relation to the action of extreme waves and experimental related loads. Physical model tests at 1:10 model scale were carried out in the wave flume facility CIEM at Universitat Politècnica de Catalunya. It has been evaluated how much these experimental results agree with the existing formulations proposed in the literature. Finally, a visual comparison between the experimental modelling and the few information of the impacts observed during the Gloria storm has been carried out. Incoming

The north-west (NW) Mediterranean coastal zone is a populous and well-developed area in which the impact of natural hazards like flash floods and coastal storms can result in frequent and significant damages. Although the occurrence and impacts of such hazards have been widely covered, few studies have considered their combined impact on the region, which would result in more damage. Within this context, this study analyses the occurrence and characteristics of compound extreme events of heavy rainfall episodes (as a proxy for flash floods) and coastal storms (using the maximum significant wave height) along the Catalan coast as a paradigm of the NW Mediterranean. Two different types of events are considered: multivariate, in which the two hazards occur at the same location, and spatially compounding, in which they occur within the same limited time window, and their impacts accumulate at distinct and separate locations. The analysis is regionally performed along a coastline extension of about 600¿km by considering seven coastal sectors and their corresponding river catchment basins. Once the compound events are analysed, the synoptic atmospheric pressure fields are analysed to determine the prevailing weather conditions that generated them. Finally, a Bayesian network is used to fully characterize these events over the territory. The obtained results show that the NW Mediterranean, represented by the Catalan coast, has a high probability of experiencing compound extreme events. Despite the relatively small size of the study area, there are significant variations in the event characteristics along the territory, with the most frequent type being spatially compound, except in the northernmost sectors where multivariate events dominate. These northern sectors also present the highest correlation in the intensity of both hazards. Three representative synoptic situations have been identified as dominant for the occurrence of these events, with different relative importance levels of the compounding drivers (rainfall and waves) and different distributions of impacts across coastal basins. Overall, results obtained from specific events indicated that heavy rainfall is related to the most significant impacts despite having a larger spatial reach. This work has been done in the framework of the M-CostAdapt (CTM2017-83655-C2-1&2-R) research project, funded by the Spanish Ministry of Economy and Competitiveness (MINECO/AEI/FEDER, UE). The authors express their gratitude to IH-Cantabria and Puertos del Estado for supplying wave data, and AEMET and SMC for supplying rain data. Our thanks are given to Montserrat Llasat-Botija for her contribution in the identification of the compound events as well as for all the information about the impacts. Peer Reviewed Objectius de Desenvolupament Sostenible::13 - Acció per al Clima

Urban floods repeatedly threaten Barcelona, damaging the city infrastructure and endangering the safety of the population. The urban planning of the city, the socioeconomic distribution, its topography, and the characteristics of precipitation systems translate into these flood events having a heterogeneous effect across the city. It means that the coping capacity has a strong dependence on local factors that must be considered when management plans are developed by the municipality. This work aims to contribute to the better knowledge of precipitation structures associated with heavy rainfall events and floods in Barcelona based on radar data and an urban rain gauge network. Radar data have been provided by the Meteorological Service of Catalonia (SMC), while precipitation data, impact data, and early warnings, have been provided by Barcelona Cicle de l’Aigua S.A. (BCASA), for the period 2013–2018. A new radar-based methodology has been developed to identify convective rainfall structures from radar reflectivity volumes (CAPPI and TOP products) to make the analysis easier. The high computing speed of the procedure allows efficient analysis of a large set of convective cells without scarifying temporal resolution of radar data. Both rainfall fields (radar and rain gauge, respectively) have been compared. Then through the identified rainfall convective structures, thunderstorm hotspots have been identified. Considering an alert indicator from BCASA and the reported incidents, episodes with the highest impact have been analysed in depth. Results show 207 significant rainfall episodes in the ROI for the six years, which are mainly concentrated between September and November. The fact that significant episodes are usually produced by highly convective rain corroborates the advantage of using radar images as a tool to detect any maxima even when no rain gauge is there. In 64 of the episodes, the level of pre-alert was achieved with a maximum frequency between August and September. The proposed algorithm shows more than 8000 centroids of convective cells from 189 cases. Whilst maximum surface reflectivity over 45 dBZ is more prone to occur near the coastline, the centroids of storm cells tend to concentrate more inland. The final objective is to improve the actions taken by the organisation responsible for managing urban floods, which have seen Barcelona recognised as a model city for flood resilience by the United Nations.

[ES] El objetivo de este trabajo es justificar y diseñar un tanque de tormentas en la zona marítima de la ciudad de Gandía, una de las más afectadas del municipio por inundaciones periódicas. En primer lugar, se corrobora que las inundaciones son el fenómeno climático más habitual y devastador en todo el mundo. Seguidamente, se estudia el riesgo que tiene España y la Comunidad Valenciana de sufrir inundaciones. Además, se presenta el tanque de tormentas como una solución válida para gestionar el exceso de aguas pluviales. A continuación, se procede al análisis hidrológico e hidráulico del barrio de Venecia, en el Grau de Gandía, la zona escogida para emplazar el depósito. Para ello, se hace uso de la metodología propuesta por la Instrucción de Drenaje Superficial 5.2-IC, y de simulaciones con el programa SWMM, para obtener un punto de partida en el volumen del tanque. Posteriormente se diseña el depósito, siguiendo las indicaciones del Manual Nacional de Recomendaciones para el Diseño de Tanques de tormenta, documento elaborado por el Ministerio de Agricultura, Alimentación y Medio Ambiente. Con el fin de evacuar el agua retenida, se ha utilizado el software Epanet para modelar el sistema de bombeo, y el programa SAP2000 para dimensionar los elementos constructivos y realizar un análisis estructural, siguiendo las indicaciones del Documento Básico de Seguridad Estructural y Acciones en la Edificación. Por último, se han elaborado los planos del tanque con el programa Autodesk Inventor, y el presupuesto con el software Arquímedes. De este estudio se concluye que la ejecución real de un proyecto de estas características sería una solución viable para contrarrestar los efectos negativos de las inundaciones en esta zona., [CA] L'objectiu d'aquest treball és justificar i dissenyar un tanc de tempestes a la zona marítima de la ciutat de Gandia, una de les més afectades del municipi per inundacions periòdiques. En primer lloc, es corrobora que les inundacions són el fenomen climàtic més habitual i devastador a tot el món. Seguidament, s'estudia el risc que té Espanya i la Comunitat Valenciana de patir inundacions. A més, es presenta el tanc de tempestes com una solució vàlida per gestionar l'excés d'aigües pluvials. A continuació, es procedeix a l'anàlisi hidrològic i hidràulic del barri de Venècia, al Grau de Gandia, la zona escollida per emplaçar el dipòsit. Per a això, es fa ús de la metodologia proposada per la Instrucció de Drenatge Superficial 5.2-IC, i de simulacions amb el programa SWMM, per obtenir un punt de partida en el volum del tanc. Posteriorment es dissenya el dipòsit, seguint les indicacions del Manual Nacional de Recomanacions per al Disseny de Tancs de tempesta, document elaborat pel Ministeri d'Agricultura, Alimentació i Medi Ambient. Per tal d'evacuar l'aigua retinguda, s'ha utilitzat el programa Epanet per modelar el sistema de bombeig, i el programa SAP2000 per dimensionar els elements constructius i realitzar una anàlisi estructural, seguint les indicacions del Document Bàsic de Seguretat Estructural i Accions en l'Edificació. Finalment, s'han elaborat els plànols del tanc amb el programa Autodesk Inventor, i el pressupost amb el programa Arquímedes. D'aquest estudi es conclou que l'execució real d'un projecte d'aquestes característiques seria una solució viable per contrarestar els efectes negatius de les inundacions en aquesta zona., [EN] The aim of this thesis is to justify and design a storm tank in the maritime area of the city of Gandia, one of the most affected areas of the municipality by periodic flooding. Firstly, it is corroborated that floods are the most common and devastating climatic phenomenon in the world. Next, the risk of flooding in Spain and the Valencian Community is studied. Furthermore, the storm tank is presented as a valid solution for managing excess rainwater. Next, the hydrological and hydraulic analysis of the neighbourhood of Venecia, in the Grau de Gandia, the chosen area to locate the tank, is carried out. To do this, the methodology proposed by the Surface Drainage Instruction 5.2-IC is used, and some simulations with SWMM programme, to obtain a starting point for the volume of the tank. Subsequently, the tank is designed, following the indications of the National Manual of Recommendations for the Design of Storm Tanks, a document produced by the Ministry of Agriculture, Food and Environment. In order to evacuate the retained water, Epanet software is used to model the pumping system, and SAP2000 programme is used to dimension the construction elements and carry out a structural analysis, following the indications of the Basic Document on Structural Safety and Actions in Buildings. Finally, the tank plans were drawn up using Autodesk Inventor program, and the budget was prepared using Archimedes software. From this study it is concluded that the real execution of a project of these characteristics would be a viable solution to counteract the negative effects of flooding in this area.

The Atmosphere-Space Interactions Monitor (ASIM) on the International Space Station (ISS) provides optical radiances and images of lightning flashes in several spectral bands. This work presents a lightning flash simultaneously observed from space by ASIM, the Geostationary Lightning Mapper (GLM) and the Lightning Imaging Sensor on the International Space Station (ISS-LIS); and from ground by the Colombia-Lightning Mapping Array (Colombia-LMA). Volumetric weather radar provides reflectivity data to help to interpret the effects of the cloud particles on the observed optical features. We found that surges in radiance in the band at 777.4 nm appear to be related mostly with lightning processes involving currents as well with branching of lightning leaders with new leader development. In cloud areas with reflectivity 7 km, these have been imaged by ASIM and GLM. But in the region with reflectivity

Els temporals són fenòmens climatològics contra els quals la humanitat hi ha estat lluitant des de sempre. Els efectes d’aquests poden ser molt variats dependent de diferents factors, tal com la direcció d’on provenen, la intensitat o la persistència amb la que actuen, és a dir, la durada. Tot i així, fins que no en succeeix un de ben intens no som realment conscients de les conseqüències que aquests poden provocar. El Gloria va deixar registres sorprenents que van deixar bocabadada a la població. No és el primer cop ni serà l´últim que un esdeveniment d’aquestes característiques impacta contra Catalunya, però no deixa de ser sorprenent la fragilitat de les infraestructures humanes i de l’entorn envers episodis d’aquesta mena. D’aquesta manera, aquest treball conté un anàlisi exhaustiu del temporal Gloria i les seves conseqüències, deixant al descobert els danys i l’empremta que va deixar. Sumant-li a més a més, un estudi en profunditat de la costa catalana i de la morfologia existent. Tractant diferents punts i analitzant diferents dades com els registres d’alçades d’ona significant, la durada o el període de retorn, seria possible caracteritzar aquesta mena d’esdeveniments i estudiar la seva probabilitat d’ocurrència, molt útil sobretot si es mira de cara al futur. En un món com l’actual que va canviant radicalment a una velocitat molt elevada, i que a més a més, es veu amenaçat per l’ombra del canvi climàtic, conèixer a fons i tractar amb temporals d’aquesta mena seria vital, sobretot a l’hora d’implementar millores a les estructures o preparar-se de manera adient per l’arribada de nous esdeveniments tan violents com aquest. Las tormentas son fenómenos climatológicos contra los cuales la humanidad ha estado luchando desde siempre. Los efectos que estos provocan pueden ser muy variados dependiendo de diferentes factores, como por ejemplo la dirección de donde provienen, la intensidad o la persistencia con la que actúan, es decir, la duración. Sin embargo, hasta que no ocurre uno muy intenso no somos realmente conscientes de las consecuencias que estos pueden provocar. El Gloria dejó unos registros sorprendentes que dejaron boquiabierta a la población. No es la primera vez ni será la ultima que un evento de estas características impacta contra Cataluña, pero no deja de ser sorprendente la fragilidad de las infraestructuras humanas y del entorno contra este tipo de episodios. De este modo, este trabajo contiene un análisis exhaustivo sobre el temporal Gloria y sus consecuencias, dejando al descubierto los daños y la huella que dejó. Sumándole, además, un estudio en profundidad de la costa catalana y de la morfología existente. Tratando diferentes puntos y analizando diferentes datos como los registros de altura de ola, la duración o el período de retorno, sería posible caracterizar este tipo de eventos y estudiar su probabilidad de ocurrencia, muy útil principalmente si se mira de cara al futuro. En un mundo como el actual que cambia radicalmente a una velocidad muy elevada, y que, además, se ve amenazado por la sombra del cambio climático, conocer a fondo y tratar con tormentas de este tipo sería vital, principalmente a la hora de implementar mejoras en las estructuras o preparase de manera adecuada para la llegada de nuevos eventos tan violentos como este. Storm are climatological phenomena that mankind has always been fighting against. The effect of these can be very varied depending on different factors, such as the direction where they come from, the intensity or the persistence, in other word, the duration of the event. However, we are not aware of the consequences they can cause until a very intense one occurs. The Gloria registered surprising records that took by surprise all the population. It was not the first time and it won’t be the last, that an event with such characteristics occurs in Catalonia, but the fragility of the human infrastructures and the environment towards phenomena of this kind is still surprising. In this way, this project covers a thorough analysis of the Gloria and its consequences, exposing all the damages and the footprint it left. Adding to this, also a study in depth of the Catalan coast and the existing morphology. By dealing with different data such as the wave height records, the duration or the return period it would be possible to characterize this type of events and study its occurrence probability. In a world that is currently changing radically fast and it’s also being menaced by the climate change, it would be vital to know all about these storms and how to deal with them, especially when refurbishing or implementing improvement to structures or preparing to properly affront these violent events in the future.

In March 2020 a convective storm erupted at planetographic latitude 76°N in the southern flank of Saturn’s long-lived hexagonal wave. The storm reached a zonal size of 4,500 km and developed a tail extending zonally 33,000 km. Two new short-lived storms erupted in May in the hexagon edge. These storms formed after the convective storms that took place in 2018 in nearby latitudes. There were no noticeable changes in the zonal profile of Saturn's polar winds in 2018-2020. Measurements of the longitude position of the vertices of the hexagon throughout this period yield a value for its period of rotation equal to that of System III of radio-rotation measured at the time of Voyagers. We report changes in the hexagon clouds related to the activity of the storms. Our study reinforces the idea that Saturn’s hexagon is a well rooted structure with a possible direct relationship with the bulk rotation of the planet. This work has been supported by the Spanish project AYA2015-65041-P and PID2019-109467GB444 I00 (MINECO/FEDER, UE) and Grupos Gobierno Vasco IT1366-19. EGM is Serra Hunter Fellow atUPC. This work has used data acquired from the NASA/ESA HST Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These HST observations are associated with program GO/DD 15262. EGM, MS, KAV and ASL thankfully acknowledge the computer resources at Mare Nostrum and the technical support provided by Barcelona Supercomputing Center (AECT-2019-2-0006). We thank all the observers who have contributed with their images to the monitoring of the atmospheric activity on Saturn during the years 2019 and 2020 and whose list and images can be found in the ALPO452 Japan and PVOL databases. Part of the amateur observations analyzed were obtained through a collaboration with Europlanet 2024 RI. Europlanet 2024 RI has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 871149.

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2021, Tutora: Maria del Carmen Llasat, The aim of this article is to study the phenomena associated with strong wind and compound events where this hazard intervenes in the region of North Girona. Of the two blocks in which this work is divided, the first one focuses on the synthesis of the literature about the most common winds in L'Empordà, floods and compound events. The second one focuses on the analysis of the situations that have affected the area based on rainfall (1950-2015), wind (1997-2018) and coastal storm (1973-2013) data provided by the M-CostAdapt project. The compound events that have been taken into account are the combination of two or three of these hazards. In total, 116 compound events took place between 1997 and 2013, mainly in September and October. The most common type was composed by heavy rain and Tramuntana wind, with a maximum wind gust between 45 and 75 Km/h. One of the strongest storms that affected Catalonia in recent years, storm Gloria, has also been analyzed

A Thesis for applying for the degree of Doctor of Philosophy in Environmental Sciences and Applied Biology. Väitekiri filosoofiadoktori kraadi taotlemiseks rakendusbioloogia erialal. Phytoplankton reflects changes in the environment and plays a vital role in biogeochemical cycles and the climate system. The thesis attempts to link the phytoplankton dynamics with the timing, intensity, and duration of the local forcing factors at different time scales. We highlight the influence of two extremes of the wind gradient – storms and atmospheric stilling, on lake environments and phytoplankton dynamics over short and long periods, several aspects of which are poorly understood. Until recently, atmospheric stilling as a climatic phenomenon has been largely overlooked in lakes studies. To fill this research gap, we focussed on a large shallow polymictic lake (Võrtsjärv, Estonia), that was affected by a 30% decrease in average wind speed since 1996, and for which a long-term (54 years) phytoplankton and hydrometeorological database was available. Further, a contradiction between the continuous decrease in the lake’s nutrient loading and an increasing trend in phytoplankton biomass emerged as a topic of interest for this thesis. We summarise how storms interact with and alter the dynamic of phytoplankton communities. Further, we highlight to what extent this impact can change the ecological processes (e.g., nutrient, carbon, and energy cycling) within lakes and their environmental conditions in the short and long term. Using Nonmetric Multidimensional Scaling ordination of phytoplankton community composition for the years 1964–2017, we revealed three distinct periods with breaking points coinciding with abrupt changes in the wind and/or water level. We introduced a concept of "light niche," a newly discovered mechanism of meteorological control over phytoplankton in light-limited shallow lakes. Combining the monthly phytoplankton data with daily data on hydrometeorological forcing factors — thermal, light, wind, and water-level regimes and using variance partitioning with linear mixed effect modelling (LME), we found that (i) the external forcing factors relevant for each phytoplankton variable could be individualised by having a similar variance partitioning among time scales as the particular phytoplankton variable; (ii) with the largest seasonal variation component, the dominant shade-tolerant filamentous cyanobacteria were most affected by seasonal factors such as solar irradiance and water level; (iii) the LME was proven appropriate for resolving the temporal cross-scale issues. Hüdrometeoroloogiliste ja kliimategurite mõju järvede fütoplanktonile: ajaskaalade olulisus Fütoplankton peegeldab muutusi keskkonnas ja mängib olulist rolli biogeokeemilises aineringes ning kliimasüsteemis. Doktoritöö uurib seoseid fütoplanktoni dünaamika ning erinevates ajaskaalades (päevane, sesoonne, aastatevaheline) toimivate tegurite ajastuse, intensiivsuse ja kestusega. Töös tuuakse esile kahe vastandliku tuulte olukorra – tormide ja tuulevaikuse mõju järvekeskkonnale ja fütoplanktoni dünaamikale, mille mitmed aspektid on seni vähe uuritud. Kuni viimase ajani on järveuuringutes suuresti tähelepanuta jäänud tuulte nõrgenemise kui kliimanähtuse mõju. Selle uurimislünga täitmiseks keskendusime suurele madalale polümiktilisele Võrtsjärvele, mida mõjutavate tuulte keskmine kiirus on alates 1996. aastast vähenenud 30% ning mille kohta on olemas pikaajaline (54 aastat) fütoplanktoni ja hüdrometeoroloogia andmebaas. Tuulte mõju uurimine võimaldas selgitada ka näilist vastuolu järve toiteainete hulga pideva vähenemise ja fütoplanktoni biomassi kasvutrendi vahel. Töö esimene osa võtab kokku teadmised tormide mõju kohta järvede fütoplanktonikoosluste dünaamikale. Tuuakse välja, kuidas tormid mõjutavad ökoloogilisi protsesse järvedes (nt toiteainete kättesaadavust, süsiniku- ja energiaringet) ning nende kaudu fütoplanktoni elutingimusi lühi- ja pikaajalises lõikes. Aastate 1964–2017 Võrtsjärve fütoplanktonikoosluse mitmemõõtmeline analüüs eristas koosluse muutustes kolm perioodi, mille murdepunktid langesid kokku tuule ja/või veetaseme järskude muutustega. Nende seoste põhjal sõnastati nn "valgusniši" kontseptsioon, mis kirjeldab varem tundmatut fütoplanktoni meteoroloogilise kontrolli mehhanismi häguse veega madalates järvedes. Kasutades enam kui poole sajandi vältel kogutud igakuiseid fütoplanktoni andmeid ja kombineerides neid igapäevaste andmetega hüdrometeoroloogiliste tegurite (temperatuur, valgus, tuul ja veetase) kohta uuriti lineaarsete segamudelite abil muutlikkuse jaotumise erinevate ajaskaalade vahel. Leiti, et fütoplanktoni erinevate rühmade jaoks olulisi välistegureid saab kindlaks teha selle järgi, et vastava rühma ja seda mõjutavate tegurite muutlikkus jaotub erinevate ajaskaalade vahel sarnastes proportsioonides. Nii mõjutasid suurima sesoonse muutlikkuse komponendiga tsüanobaktereid enim sesoonsed tegurid, flagellaatide puhul, sarnaselt tuulega, ulatus aga juhusliku ja lühiajalise varieeruvuse komponent 80%-ni. Kokkuvõttes osutusid lineaarsed segamudelid sobivaks tööriistaks erinevates ajaskaalades toimivate tegurite mõju uurimiseks. Publication of this thesis is supported by the Estonian University of Life Sciences.

Convective activity in Catalonia (northeastern Spain) mainly occurs during summer and autumn, with severe weather occurring 33 days per year on average. In some cases, the storms have unexpected propagation characteristics, likely due to a combination of the complex topography and the thunderstorms’ propagation mechanisms. Partly due to the local nature of the events, numerical weather prediction models are not able to accurately nowcast the complex mesoscale mechanisms (i.e., local influence of topography). This directly impacts the retrieved position and motion of the storms, and consequently, the likely associated storm severity. Although a successful warning system based on lightning and radar observations has been developed, there remains a lack of knowledge of storm dynamics that could lead to forecast improvements. The present study explores the capabilities of the radar network at the Meteorological Service of Catalonia to retrieve dual-Doppler wind fields to study the dynamics of Catalan thunderstorms. A severe thunderstorm that splits and a tornado-producing supercell that is channeled through a valley are used to demonstrate the capabilities of an advanced open source technique that retrieves dynamical variables from C-band operational radars in complex terrain. For the first time in the Iberian Peninsula, complete 3D storm-relative winds are obtained, providing information about the internal dynamics of the storms. This aids in the analyses of the interaction between different storm cells within a system and/or the interaction of the cells with the local topography.

Coastal risk assessments rely on proper quantification of storm-induced erosion and flooding, and often involve calculations via numerical models. When the real time-series data of a storm are not available as forcing conditions and only bulk information is accessible, synthetic simplified time-evolutions are assumed. The most common approach in coastal studies uses a symmetric triangular storm shape, characterised by the assumptions that the peak of the waves occurs in the middle of the storm, and that the forcing varies linearly. This study aims to investigate this additional source of uncertainty in hazard estimation, using the XBeach-1D model, to assess the differences in simulated erosion and flooding associated with real and synthetic storm definitions. Analysis is performed for real conditions ranging from moderate to extreme at the Northern Adriatic and North-Western Mediterranean coasts, using beach profiles ranging from dissipative to reflective. The storm definitions generate considerable differences in terms of wave power and timing at the peak of the storm. When synthetic storms were applied, coastal hazards were not adequately reproduced in most of the simulated cases. The energy of the storms, profile characteristics, local storm climates, and water levels did not consistently influence the differences between the synthetic- and reality-based outputs. The work of E. Duo was supported by a PhD grant at the Department of Physics and Earth Science of the University of Ferrara, additional funding from the contribution “5 per mille assegnato all’Università di Ferrara - dichiarazione dei redditi dell'anno 2013” assigned through the “Bando Giovani Ricercatori 2016″ of the University of Ferrara, and the EU H2020 ANYWHERE project (GA 700099; www.anywhere-h2020.eu). The work of M. Sanuy and J.A. Jiménez has been done in the framework of the M-CostAdapt (CTM2017-83655-C2-1-R) research project (MINECO/AEI/FEDER, UE). Marc Sanuy was supported by a PhD grant from the Spanish Ministry of Education, Culture and Sport.

Treball d'investigació/Fi de màster. Tutor: Dr. Dídac Pujol. Aquest treball consisteix en una traducció de l’anglès al català del relat “An Honest Woman”, de l’autora nord-americana contemporània Ottessa Moshfegh. Aquesta traducció va dirigida al mateix tipus de destinatari que el text original, és a dir, un públic general adult. Els objectius del treball són: 1) oferir una traducció tan adequada al text original com sigui possible; 2) que el text català tingui el mateix efecte en el lector que el text original; 3) fer un comentari de la traducció, valorant l’adequació de les tècniques de traducció utilitzades per resoldre alguns dels principals obstacles amb què m’he trobat a l’hora de traduir: la cursiva, el gerundi, el vocabulari relacionat amb tempestes i l’ús del guió en els diàlegs. This paper consists of a translation from English into Catalan of the short story “An Honest Woman”, by Ottessa Moshfegh, a contemporary American writer. This translation is directed at the same audience as the source text, a general adult public. The aims of this project are: 1) to present a translation as adequate to the source text as possible; 2) to create the same effects on the target text reader as the original; 3) to write a translation commentary, taking into account the translation strategies used to solve the main translation problems I encountered when translating the source text: italics, gerunds, vocabulary related to thunderstorms, and the use of dashes in dialogue.

Synergistic remote sensing of the atmosphere, combined with adaptive techniques, offers unprecedented opportunities to characterise the evolution of key atmospheric features such as the Atmospheric Boundary Layer (ABL). Using long-duration, high-resolution, profiling observations from active and passive ground-based remote sensing systems during the Verification of the Origins of Rotation in Tornadoes Experiment{Southeast (VORTEX-SE) 2017 field campaign, an attempt is made to characterise ABL development over distinct regions that are well known for their relatively high tornado frequency. In this study, observing systems include an S-band radar, Vaisala CL-31 ceilometer, Doppler Wind lidar (DWL) and radiometric observations from the Collaborative Lower Atmosphere Mobile Profiling System (CLAMPS). In this work, ABL height (ABLH) tracking over the diurnal cycle, and - up to a point - its disambiguation over selected non-precipitating case examples, are attempted. Different observational sets are used, namely, radar reflectivity observations assimilated into a Kalman filter, DWL profiles of the vertical velocity, and virtual potential temperature profiles, as well as radiosoundings and cloudbase reference information collected during Intensive Observation Periods (IOP) carried out in VORTEX-SE, Alabama during 2017. Limitations and advantages of each system are discussed. This work was supported by NOAA grants NA1501R4590232 and NA16OAR4590209, and by the Purdue University Dept. of Earth, Atmospheric, and Planetary Sciences (EAPS). CommSensLab-UPC (Excellence UnitMDM-2016-0600 funded by the Agencia Estatal de Investigación, Spain) collaborated via Spanish Gov.– EURegional Development Funds, ARS project PGC2018-094132-B-I00 and ACTRIS-PPP project GA-739530. The Spanish National Science Foundation (Ministerio de Ciencia, Innovación y Universidades) funded doctoral grant PRE2018-086054 hold by M.P. Araujo da Silva.

Sol·licitant de l'informe: Barcelona Cicle de l'Aigua, S.A.

Africa is one of the most productive lightning regions on Earth, yet it has a lower TGF-to-lightning ratio especially compared with Central America. In this paper we have analyzed the global distribution of different meteorological parameters in order to explain the TGF/lightning ratio asymmetry. We show here that a drier surface and larger CAPE in Africa may produce thunderstorms with intense electric charge regions but elevated in the atmosphere and closer to each other, which allows for higher flash rates and less energetic, shorter and smaller flashes. The results we present here suggest that continental thunderstorms in Africa more rarely fulfill the lightning and thundercloud requirements for TGF production inferred from observations and models.

Charge structure derived from lightning leader development of tropical thunderstorms comprising equatorial latitudes of < ±10° has not been investigated yet. In this work, using a Lightning Mapping Array (LMA) installed in northern Colombia, the charge structure, lightning leader initiations and the cloud-to-ground strokes rates of two thunderstorms have been analyzed. Additionally, radar information is also included. The identification of the charge regions has been obtained by analyzing the propagation of lightning leader developments. Flashes initiate between 4 and 15 km altitude. High initiation rates are different in the two storms. In one case the high rates are found between 8 and 13 km. In the other these are found between 10 and 15 km. The storms show typical tripolar structure where the upper positive charge is present at 10 to ~15 km, the mid-level negative charge is found between 6 and 9 km and the lower positive charge between 4 and 6 km altitude. Intracloud lightning flashes with inverted polarity have been identified for short period. In other periods, screening layer flashes have been detected at 14-15 km. The overall results show that the charge structures in the two Colombian storms are similar to the ones reported in North-Central Florida, but with a significant difference being the more than 2 km higher initiation altitude in Colombia. The vertical configuration of the charge regions and the leader development of these thunderstorms might help to explain the occurrence of Terrestrial Gamma-ray Flashes in tropical thunderstorms

Sol·licitant de l’informe: Gerència de Medi Ambient i Serveis Urbans

Treballs Finals de Grau en Geografia, Facultat de Geografia i Història, Universitat de Barcelona, Curs: 2018-2019, Tutor: Mª Carmen Moreno, El objetivo fundamental de este trabajo es el de establecer la validez de los datos de detección de descargas eléctricas atmosféricas totales (nube/nube y nube/tierra) como fuente fiable de información geofísica Un objetivo secundario será el de establecer la potencial utilización de dicha fuente de información geofísica para la prospección de depósitos subterráneos de agua en regiones áridas y semiáridas. Como hipótesis principal de trabajo se plantea que la recurrencia de las descargas eléctricas sobre una determinada zona geográfica pueda estar relacionada con la estructura geológica del subsuelo.

Sol·licitant de l’informe: Gerència de Medi Ambient i Serveis Urbans

Meteorological conditions and thunderstorm characteristics related to lightning threats to wind turbines are discussed in this paper. Due to the rotating blades, wind turbines may be regarded peculiar tall objects, more susceptible to lightning strikes than other tall man-made structures. In the present study, Lightning Mapping Array and weather radar observations allowed to draw a clear picture of the thunderstorm characteristics leading to lightning strokes to wind turbines, in a coastal area of the Mediterranean basin. Results showed that lightning threats to wind turbines tend to occur during transitional periods (spring and autumn), although the main thunderstorm activity concentrates in the warm summer months. Thunderstorms with downward strokes to wind turbines presented particular features, like a limited vertical development and a dominant lower positive charge layer. Downward cloud-to-ground strokes hitting wind turbines were mainly of negative polarity and with peak currents above the average. On the other hand, conditions for self-initiated upwards from wind turbines resemble those reported in Japan and the U.S winter thunderstorms, with low-cloud based large electrified stratiform regions. These particular conditions, leading to lightning threats to wind turbines, should be properly included in lightning protection standards.

Aquest article recull el balanç meteorològic del 2017 a l’Alt Empordà, i així es manté la sèrie de resums meteorològics que aquesta revista Annals va iniciar l’any 2014, amb l’objectiu de crear un registre històric de dades i informació meteorològica que amb el pas del temps prendrà un valor climàtic més gran i permetrà conèixer millor l’evolució del clima a la comarca en les darreres dècades. Podrà esdevenir una bona eina analítica per desenvolupar estudis de la comarca dins del context del canvi climàtic. L’article conté un resum meteorològic que té l’objectiu d’explicar i il·lustrar, demanera especialment gràfica, el comportament de lameteorologia el 2017,mostrant tant les dades mitjanes com els valors extrems de temperatura, precipitació i vent a la comarca. Es fa un repàs de les situacions meteorològiques que han presentat més interès atmosfèric, i es mostren les diferències espacials que s’han produït en el territori en el repartiment de les quantitats de pluja i dels valors de temperatura tant mitjans comextrems. Globalment, el 2017 s’ha presentat a la comarca molt càlid i sec, certificant la clara tendència dels darrers anys en les anomalies de la pluja i de la temperatura. La tramuntana va tenir una presència important, sobretot a la tardor i a principis de l’hivern., This article presents a meteorological balance of 2017 in Alt Empordà, and thereby continues the series of meteorological summaries that this journal started in 2014, with the aim of creating a historical record of data and weather information which, in time, will obtain important climatic value and allow us to understand the evolution of climate in the region throughout the last decades. It can become a vital tool for local studies on climate change. This meteorological summary aims to explain and illustrate through graphics the behaviour of meteorology in our region throughout 2017, showing both average data and the extreme values of temperature, precipitation and wind. Meteorological situations of most atmospheric interest are reviewed and as well as spacial differences within the territory of quantities of rain and temperature values, both average and extreme. Overall, 2017 was a warm and dry year in the region, certifying the clear tendency in recent years of unusual rains and temperatures. The tramuntana north wind had an important presence especially in autumn and beginning of winter.

[cat] Catalunya, i en concret el Pla de Lleida, són zones sovint afectades per les pedregades. En general, els episodis més severs i freqüents es produeixen des de finals de la primavera fins a principis de la tardor. Aquest període coincideix amb el moment en què determinats cultius de la zona són altament vulnerables, degut al seu cicle vegetatiu. La importància a nivell econòmic i social que tenen les pedregades al territori català, com també la complexitat del fenomen, ha comportat que nombrosos científics hagin estudiat el tema des de diferents punts de vista. En aquesta tesi s'ha aprofundit en temes de diagnosi i predicció, amb una fase preliminar d'anàlisi per conèixer la distribució espacial i estacional de les pedregades a la zona. En temes de diagnosi, i amb l'objectiu de conèixer el diàmetre de la pedra obtinguda en indrets sense possibilitat d'observació directa, s'ha aplicat un mètode d'estimació de la mida de la pedra. Els resultats més òptims s'han aconseguit a partir del mètode cokriging universal, combinant poques dades puntuals, les observacions en superfície, amb una variable contínua secundària, que en aquest cas es tracta d'informació radar. Els valors estimats més propers a la realitat s'han aconseguit utilitzant el producte vertically integrated liquid (VIL) de la imatge no corregida del radar de la Panadella (CDV). Pel que fa al camp de la predicció, s'ha aplicat l'algorisme lightning jump (LJ), amb importants modificacions respecte a la metodologia original i adaptant-lo a les necessitats operatives del Servei Meteorològic de Catalunya (SMC), amb l'objectiu de pronosticar temps sever a curt termini al nostre país. El percentatge d'encert d'aquesta eina davant aquests fenòmens és molt elevat. A més, un altre fet important és que el percentatge d'error és molt baix. La distància de temps en què s'alerta de possible temps sever, coneguda com a lead time, inicialment, s'ha mogut entre 15 i 45 minuts amb un pic als 20 minuts. Posteriorment, a partir de la incorporació del paràmetre de la multiplicitat en l'algorisme, aquesta distància temporal s'ha incrementat fins a 120 minuts. L'anàlisi de la predicció segons la severitat de la tempesta o, altrament dit, segons el diàmetre de la pedra ha estat costosa i se n'han extret poques conclusions discriminatòries, a partir dels casos estudiats. En conjunt, l'activitat elèctrica i el comportament d'alguns paràmetres radar no han mostrat diferències significatives per arribar a determinar si una tempesta va acompanyada de pedra grossa o petita, en el moment que salta una alerta de LJ. Només el perfil de reflectivitat seria considerat una característica determinant que pot facilitar aquest tipus de pronòstic. Durant les campanyes més recents, l'eina de LJ ha estat aplicada en l'operativa de l'Equip de Predicció i Vigilància (EPV) de l’SMC. Inicialment, es va posar en mode de prova, i va passar, vistos els bons resultats, a l'operativa en temps real. Aquest seguiment ha permès portar un control diari de l'eina i trobar millores en l'algorisme. Per tant, es demostra l'aplicabilitat de la present tesi en tasques del dia a dia. La multiplicitat, esmentada prèviament, ha estat una característica afegida recentment, la qual ha permès pronosticar pedregades de mida inferior als 2 cm, precipitacions intenses, com també millora la predicció de temps sever. Finalment, per cobrir la manca d'observacions en determinades situacions de severitat, s'ha dut a terme la campanya de ciència ciutadana Plega/Caça la pedra. S'han obtingut uns resultats satisfactoris triplicant quasi el nombre d'observacions respecte d'anys anteriors. Aquesta quantitat d'observacions ha permès fer un millor control i validació de l'eina de LJ., [eng] The hail is a common severe weather phenomenon in Catalonia, producing important damages in different society environments. Nowadays, there are a lot of doubts about its forecast and, although, on respect the diagnosis of size hail. Both uncertainties are due to the high variability of hailstorms. This PhD is based on the analysis of thunderstorms associated to severe weather (large hail, tornados or waterspout, downburst and strong wind gust). The PhD has been focus on answering some of the existent doubts. On one hand, a diagnosis forecast tool has been applied to obtain information about hail diameter recorded after that one thunderstorm had affected an area without any direct measure instrument. On the other hand, a severe forecast tool named “Lightning jump” has been studied, adapted and put in operational. This algorithm permits to do a nowcasting forecast about severe weather phenomena in one hour in advance. It is an innovation PhD considering the incorporation of diagnosis and forecast new tools. Moreover, some of them are used currently in the Servei de Meteorològic de Catalunya for severe weather forecasting purposes.

Extreme events, such as wave-storms, need to be characterized for coastal infrastructure design purposes. Such description should contain information on both the univariate behaviour and the joint-dependence of storm-variables. These two aspects have been here addressed through generalized Pareto distributions and hierarchical Archimedean copulas. A non-stationary model has been used to highlight the relationship between these extreme events and non-stationary climate. It has been applied to a Representative Concentration Pathway 8.5 Climate-Change scenario, for a fetch-limited environment (Catalan Coast). In the non-stationary model, all considered variables decrease in time, except for storm-duration at the northern part of the Catalan Coast. The joint distribution of storm variables presents cyclical fluctuations, with a stronger influence of climate dynamics than of climate itself.

In this work we study the belief in the existence of tempestarii or inmissores tempestatum in Hispania in Late Antiquity. Despite the scarcity of sources on this subject, those that do exist suggest that, in the Iberian Peninsula, people believed individuals to be capable of causing storms with their own will. The sources in question include two Chindaswinth laws, which express the authorities’ concerns over “storm-makers” capable of ruining the crops of others. In addition, two epigraphic testimonies, reproducing magic formulae engraved on slate (with an imprecise date between the 8th and 10th centuries) suggest the presence in Hispania of the defensores mentioned by Agobard of Lyon in the Frankish Kingdom, magicians who claimed to know how to move storms away from the fields. These scarce sources can be complemented by information from Frankish Gaul sources, and particularly the aforementioned Agobard. Finally, we consider how the Church sought to combat these beliefs, appropriating and adapting them to its own thought, and replacing the evil spirits that caused storms with Satan and his demons, and the divinities that protected the fields with Christian saints and angels., En el presente trabajo estudiamos la creencia en la existencia de tempestarii o inmissores tempestatum en la Hispania tardoantigua. A pesar de la escasez de fuentes para dicho tema, éstas nos permiten aseverar que en la península Ibérica la gente reconocía como reales los individuos capaces de provocar tormentas con su sola voluntad. Estas fuentes corresponden a dos leyes de Chindasvinto, que manifiestan la preocupación de las autoridades por los «hacedores de tormentas» que arruinaban las cosechas de terceros. Además, dos testimonios epigráficos, que reproducen fórmulas mágicas grabadas sobre pizarra (con una cronología imprecisa que corre entre los siglos VIII y X), sugieren la presencia en Hispania de los defensores mencionados en el reino franco por Agobardo de Lyon, magos que presumían de alejar las tempestades de los campos de cultivo. La pobreza de estas fuentes puede completarse con la información proporcionada por fuentes de la Galia franca, entre las que destaca el mencionado Agobardo. Finalmente, vemos cómo la Iglesia combatió estas creencias apropiándose de ellas y adaptándolas a su pensamiento, sustituyendo los malos espíritus que provocaban tormentas por Satán y sus demonios, y las divinidades que protegían los campos por los ángeles y los santos cristianos.

Sol·licitant de l’informe: Parc d'Atraccions del Tibidabo, S.A.

Aquest article recull el detall d’un balanç meteorològic del 2016 a l’Alt Empordà, i dona continuïtat a la sèrie de resums meteorològics que aquesta publicació Annals va iniciar l’any 2014, amb l’objectiu de crear un registre històric de dades i informació meteorològica amb valor climàtic que ens permet mirar enrere i explorar quina és l’evolució del clima a la comarca. Es tracta d’un resum meteorològic que té l’objectiu d’explicar i il·lustrar el comportament de la meteorologia el 2016 a la nostra comarca, mostrant tant les dades mitjanes com els valors extrems de temperatura, precipitació i vent. Així mateix, es destaquen alguns aspectes meteorològics que han estat d’interès i es posa l’èmfasi en les diferències territorials de la meteorologia entre les zones de muntanya, de la plana i de la costa, com a mostra de la diversitat climàtica d’aquest territori. Globalment, l’any 2016 s’ha presentat a la comarca càlid i sec, dos qualificatius que semblen força habituals en els darrers anys., This article collects the detail of a meteorological balance of 2016 in Alt Empordà, and continues the series of meteorological summaries that this journal began in 2014, with the aim of creating a historical record of data and weather information with climatic value that allows us to look back and explore the evolution of the climate in the region. This meteorological summary aims to explain and illustrate the behaviour of meteorology in our region throughout 2016, showing both average data and the extreme values of temperature, precipitation and wind. Likewise, it emphasizes some meteorological aspects that have been of interest and territorial differences of meteorology between the mountain, plain and coastal areas, showing the climatic diversity of this territory. Overall, 2016 was a warm and dry year, two qualifications that seem quite common in recent years.

The present study makes use of cloud-to-ground lightning, three-dimensional mapping from a Lightning Mapping Array and Doppler C-band radar observations to analyze the lightning trends and the underlying electrical charge structure of a large-hail bearing storm that produced important damages on the local agriculture. The analysis reported an extremely active storm, evolving through distinct phases, which stood out from a multicell structure to finally become a supercell. The onset of newer regions of convective development interacting with the main cell made the charge structure to be rather complex during some stages of this long-lived hailstorm. Evidence suggests the presence of regions with the charge layer being inverted from that of normal, non-severe convective storms, producing predominantly positive cloud-to-ground lightning. The analysis also suggests that strong cloud signals were misclassified as low peak current single-stroke negative cloud-to-ground flashes, masking the predominant positive nature of the storm.

Sprites are Transient Luminous Events (TLEs) that can extend vertically from 40 to 90 km and horizontally over several tens of km to form clusters of individual or multiple column or/and carrot-shaped luminous elements. They can even extend over more than 100 km in the form of sequential luminous emissions that are called “dancing sprites”. Their optical detection and other parameters describing the storm and the lightning activity associated allow us to understand their conditions of production and their links with the lightning activity. Our observations confirm some characteristics of the sprites and put forward others: (i) the sprites are essentially produced above the stratiform region of the Mesoscale Convective Systems after positive cloud-to-ground lightning flashes that produce large Charge Moment Change (CMC), with a delay of as much shorter than the impulsive CMC (iCMC) is large. (ii) The dancing sprites reflect the timing and the location of the successive lightning strokes that generate them. (iii) The sprite elements can be shifted from the stroke location when their delay is large. (iv) Bright sprites produce current signatures in ELF radiation a few milliseconds (< 5 ms) after the positive strokes that generate them.

Màster de Meteorologia, Facultat de Física, Universitat de Barcelona, Curs: 2014-2015, Tutors: Mª del Carme Llasat Botija, Tomeu Rigo Ribas, One of the most adverse weather phenomena in Catalonia are thunderstorms producing severe weather phenomenon like heavy rainfalls, hail storms, or tornadoes. Sometimes, these thunderstorms seem to have marked paths although in some cases these trajectories vary sharply, changing completely the movement directions that have previously followed, either breaking into several cells, or joining into a bigger one. In order to identify the main features of the developing process of thunderstorms and the anomalous movements that these may in some cases follow, this paper presents a methodology that follows 3 main steps; previous classification of the events, cell identification, and finally, tracking of the cells identified. The methodology combines radar and satellite images.

Màster de Meteorologia, Facultat de Física, Universitat de Barcelona, Curs: 2015-2016, Tutor: Joan Bech, Combinant la informació que proporcionen les dades d’un sistema de detecció de llamps, alguns productes de radar i perfils de temperatura extrets de radiosondatges, es determina amb precisió la posició i instant de temps en què té lloc l’inici de l’activitat elèctrica en un conjunt de 18 casos d’estudi seleccionats de tempestes que s’originen a prop del Delta de l’Ebre. Estudiant els perfils de reflectivitats i la distribució vertical de temperatura en aquests punts es caracteritzen les variables analitzades per tal de trobar quins valors són més probables que s’assoleixin en l’instant en què s’enregistra la primera descàrrega d’una tempesta. Els resultats indiquen que en l’altitud a la qual s’inicia l’activitat elèctrica, el valor més probable de la temperatura és de -10ºC, i la reflectivitat màxima més freqüent del perfil vertical és de 40 dBZ, que es troba als nivells corresponents a -10ºC, on s’espera que estiguin situades les partícules de calabruix, i al nivell de 5ºC, degut a un efecte de banda brillant. D’altra banda, localitzant els nivells on es troben certs valors de reflectivitat, la combinació que es dóna més freqüentment en els instants inicials és de 35 dBZ al nivell de -15ºC. Altres combinacions que es repeteixen indiquen la presència d’una separació de càrregues dins del núvol en forma de distribució tripolar. Finalment, es troba que les cel·les tenen una extensió vertical mínima de 7 km, podent superar els 10 km, en l’instant en què es detecta el primer llamp

From June 2008 to January 2016 nearly 800 elves have been recorded by a low-light camera in northeastern Spain. Elves occur in this region mainly over the lower topped cold air mass maritime thunderstorms, peaking from November to January. Cloud-to-ground strokes still produce elves when maritime winter storms are carried inland, suggesting that the cold season thunderstorm charge configuration favors strokes with large electromagnetic pulses. Altitudes of 389 elves were determined using optical data combined with a lightning location network. The overall median altitude was 87.1 km, near the typical OH airglow height, but average heights during individual nights ranged between 83 and 93 km. The lower elve nights (~84 km) occurred during slightly elevated geomagnetic conditions (Kp >3-, Ap-index >10). Elve altitude often shifts by several kilometers during the night, apparently in response to changing background conditions in the upper mesosphere.

Terrestrial Gamma ray Flashes (TGFs) have been known since 20 years ago, but since the first moment of the discovery it was clear that they were related to lightning and thunderstorms. The latest studies revealed that TGFs could be produced during the first stages of the lightning within thunderclouds by a process which is very similar to the X-ray emissions from natural lightning observed from ground or discharges in high voltage laboratory. The study of such phenomena will help to extend and complete the knowledge about lightning and electrical discharges. This study compares geographic, monthly and diurnal cycle global distributions of TGFs and lightning. A fourth region with enhanced production of TGFs has been identified apart from the other three regions previously identified. This analysis further investigates the relation between TGFs, lightning activity and thunderstorms. Moreover, we have seen that the TGF/lightning ratio is different in each region which could be explained by meteorological differences between regions and not by differences in regional lightning detection efficiency. For the first time, meteorological conditions and lightning activity have been compared among situations where a satellite with capability to detect TGFs did or did not detect them. The objective is to identify the best atmospheric conditions for TGF production. We have established that electrification processes associated with strong updrafts and high CAPE values are important to create the best atmospheric conditions that favours TGF generation. In the second part of the study we defined criteria for the TGF/lightning correlation in time. Using these criteria we have identified 90 correlations in South America. Depending on the time difference between TGF and lightning the correlations have been grouped into different categories. For each category the relation between TGF and lightning was justified based on examples of upward propagation of negative leaders detected by a VHF lightning mapping network, consistent with the currently most accepted production theories. We were able to identify associated thunderstorms in 32 of 90 correlation cases. We have analysed the thunderstorm development stage at the moment of TGF production, the vertical extent and areal extent. It was found that analysed thunderstorms shows preferences for TGF production during developing or mature stages and great vertical extension what agrees with situations with strong updrafts and high CAPE values determined in the first part of the study. The last part presents an analysis of the association between X-ray events and lightning registered at the Eagle Nest Tower in the Pyrenees. We have determined that downward negative lightning seems to be the only candidate for x-ray emissions. The theories that support this hypothesis could also explain TGF production, specifically, as in examples of upward negative leaders shown in the previous section. We have also studied whether the high energy background radiation increased in association with thunderstorm electrification. However, in the cases analysed this increase has been associated with radon-ion daughters., Las emisiones de rayos gamma terrestres (TGFs) se conocen desde hace apenas 20 años, pero desde el primer momento se vio claramente su relación con los rayos y tormentas. Los últimos estudios revelan que se podrían producir durante las primeras fases de los rayos en el interior de las nubes por un proceso que sería muy similar a la emisión de rayos X por rayos naturales observados desde suelo o por descargas en el laboratorio de alta tensión. El estudio de estos fenómenos ayudará a ampliar y completar los conocimientos sobre el fenómeno del rayo y de las descargas eléctricas. En primer lugar se han comparado las distribuciones globales geográficas, mensuales y el ciclo diurno de TGFs y rayos. Se ha identificado una cuarta región de producción de TGFs a parte de las tres ya identificadas previamente. Con este análisis se ha contribuido principalmente a la confirmación de las correlaciones de los TGFs con la actividad de rayos y tormentas. Además, se ha visto que las ratios de TGF/rayo varían en las distintas regiones con lo que es probable que se pueda explicar por las diferencias meteorológicas entre ellas y no por diferencias regionales en la eficiencia de detección de rayos. Por primera vez se han analizado las condiciones meteorológicas y actividad de rayos en aquellas situaciones en que un satélite con capacidad para detectar TGFs no los detectaba y se han comparado con aquellas situaciones en que si se detectaron. El objetivo es el de distinguir las mejores condiciones atmosféricas para su producción. Se ha determinado que los procesos de electrificación asociados a fuertes corrientes ascendentes y altos valores de CAPE son importantes para crear las mejores condiciones atmosféricas que favorecen la generación de TGFs. En la segunda parte se definido un criterio para la correlación temporal entre rayos y TGFs. Con este criterio se han identificado un total de 90 correlaciones en Sudamérica. En función de la diferencia temporal entre el rayo y el TGF se han agrupado en distintas categorías. Para cada una de ellas se ha intentado justificar la relación entre el TGF y el rayo en base a ejemplos de rayos detectados por una red VHF y a las teorías de producción más aceptadas hasta la fecha. De 32 de estos casos de correlación se ha podido identificar y analizar la tormenta asociada. Se ha analizado la fase de desarrollo de la tormenta en el momento de la producción del TGF, la extensión vertical y la extensión horizontal. Se ha visto que las tormentas analizadas muestran una preferencia para la producción de TGFs en las fases de desarrollo o madurez y de gran extensión vertical que concuerda con situaciones de fuertes corrientes ascendentes y altos valores de CAPE determinados en el estudio previo. En la última parte se ha analizado eventos registrados en la torre instrumentalizada del Nido del Águila en los Pirineos. Estos eventos corresponden a rayos naturales y radiación X. Se ha determinado que los líderes negativos parecen ser los únicos candidatos para la emisión de rayos X. Las teorías que soportan esta hipótesis podrías explicar la producción de TGFs y, en concreto, los casos reportados en el estudio anterior. Se ha estudiado también si el aumento de la radiación de fondo de alta energía está asociado a la posible electrificación de las tormentas. En el caso analizado se ha asociado este aumento con los descendientes radiactivos de la cadena de desintegración del radón

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Any: 2014, Tutor: Joan Bech, Cloud-to-ground stroke data have been analysed for the years 2010-2012 for the Cata- lan region. These strokes have been grouped together into lightning ashes using a hierarchical clustering method, with two di erent approaches to the clustering radius, as the objective of the study was to evaluate di erent clustering methods. The results for the two approaches were com- pared with the results from a step-by-step method, giving us di erences of 2% and 7% in the nal number of lightning ashes. Using di erent values for the lightning ash window and lightning spa- tial radius the multiplicity values from the clustering methods results ranged from 1.6 to 2.0. These results can improve the reliability of studies where the number of lightning ashes is important such as in severe weather case studies or in climatological rainfall to lightning ratio analysis.

This paper presents thunderstorm electrostatic field measurements carried out by electric field mills located at mountainous regions in Spain and Colombia. The profile of electric field changes ¿E due to lightning vs distance is computed by using data from a lightning location system. The effect of the topography on the ¿E vs distance profile is studied in order to identify necessary adjustments for field mills used as lightning warning systems affects by topographycal factors.

RHESSI and AGILE TGFs distributions in the period 2009-2012 are compared. Analysis of differences in geographical, hourly, monthly distributions of the three main TGF production regions in Earth due to differences in lightning production and ITCZ movement is presented. A fourth region producing TGFs over Pacific not reported before is also analysed. Second analysis has been performed in order to identify preferable meteorological conditions for TGF production. Some publications suggested that regional differences in lightning/TGF ratio may be due to differences in meteorological thunderstorm and lightning production. All AGILE passes over South America (SA) in 2009-2012 has been studied. No special meteorological features characteristic of SA has been identified. TGFs are detected in situations with many lightning, thunderstorms, high CAPEs and high Top Clouds. TGFs are more probable to be detected in active situations.

11 pages

A heavy precipitation event swept over Catalonia (NE Spain) on 8 March 2010, with a total amount that ex- ceeded 100mm locally and snowfall of more than 60cm near the coast. Unusual for this region and at this time of the year, this snowfall event affected mainly the coastal region and was accompanied by thunderstorms and strong wind gusts in some areas. Most of the damage was due to"wet snow", a kind of snow that favours accretion on power lines and causes line-breaking and subsequent interruption of the electricity supply. This paper conducts an interdisciplinary analysis of the event to show its great societal impact and the role played by the recently developed social networks (it has been called the first"Snowfall 2.0"), as well to analyse the meteorologi- cal factors associated with the major damage, and to propose an indicator that could summarise them. With this aim, the paper introduces the event and its societal impact and com- pares it with other important snowfalls that have affected the Catalan coast, using the PRESSGAMA database. The sec- ond part of the paper shows the event"s main meteorological features and analyses the near-surface atmospheric variables responsible for the major damage through the application of the SAFRAN (Système d"analyse fournissant des renseigne- ments atmosphériques à la neige) mesoscale analysis, which, together with the proposed"wind, wet-snow index" (WWSI), allows to estimate the severity of the event. This snow storm provides further evidence of our vulnerability to natural haz- ards and highlights the importance of a multidisciplinary ap- proach in analysing societal impact and the meteorological factors responsible for this kind of event.

En aquest article s’ha realitzat una enquesta de percepció sobre processos de caigudes de blocs i esllavissades a la població de pescadors professionals i recreatius de l’illa de Menorca. Els resultats indiquen els indrets de la costa on els pescadors aprecien fenòmens geomorfològics de caigudes de blocs. A l’hora, ens permet tenir un punt de partida per a l’estudi dels processos inestables a la costa rocosa de Menorca. S’ha pres una mostra representativa de 48 enquestes a pescadors professionals i 88 enquestes a pescadors recreatius delimitant 39 zones amb processos actius. En el cas dels pescadors professionals s’han pres com a zones de mostreig els ports base de: Maó, sa Nitja, Macaret, Fornells, Ciutadella, Biniancolla, es Grau, Alcalfar, Canutells i cales Fonts. Amb el resultat de les enquestes es troben algunes respostes associades a la manca de blocs de tempesta o tsunami a les costes rocoses que ens han animat a explorar tot el perímetre de la costa de Menorca., This paper has conducted a survey on fisherman perception about cliff falling blocks processes and their location. It is an starting point for the study of unstable processes on the rocky coast of Menorca. It has taken a representative sample of the fishermen of the island, with 48 s professional and 88 recreational, analyzing 39 localities. Information provided by commercial fishermen have been taken in homeports: Maó, sa Nitja, Macaret, Fornells, Ciutadella, Biniancolla, es Grau, Alcalfar, Canutells i cales Fonts. Results show the lack of storm or tsunami blocks, of the rocky shores in some areas that we have been encouraged to explore the entire perimeter of the coast of Menorca.

13 pages, 7 figures, supporting information in https://doi.org/10.1371/journal.pone.0053742, Extreme events are rare, stochastic perturbations that can cause abrupt and dramatic ecological change within a short period of time relative to the lifespan of organisms. Studies over time provide exceptional opportunities to detect the effects of extreme climatic events and to measure their impacts by quantifying rates of change at population and community levels. In this study, we show how an extreme storm event affected the dynamics of benthic coralligenous outcrops in the NW Mediterranean Sea using data acquired before (2006-2008) and after the impact (2009-2010) at four different sites. Storms of comparable severity have been documented to occur occasionally within periods of 50 years in the Mediterranean Sea. We assessed the effects derived from the storm comparing changes in benthic community composition at sites exposed to and sheltered from this extreme event. The sites analyzed showed different damage from severe to negligible. The most exposed and impacted site experienced a major shift immediately after the storm, represented by changes in the species richness and beta diversity of benthic species. This site also showed higher compositional variability immediately after the storm and over the following year. The loss of cover of benthic species resulted between 22% and 58%. The damage across these species (e.g. calcareous algae, sponges, anthozoans, bryozoans, tunicates) was uneven, and those with fragile forms were the most impacted, showing cover losses up to 50 to 100%. Interestingly, small patches survived after the storm and began to grow slightly during the following year. In contrast, sheltered sites showed no significant changes in all the studied parameters, indicating no variations due to the storm. This study provides new insights into the responses to large and rare extreme events of Mediterranean communities with low dynamics and long-lived species, which are among the most threatened by the effects of global change. © 2013 Teixido et al., This study has been funded by the Agence National de la Recherche (Medchange project) and Total Foundation (medDIVERSA project, http://meddiversa.medrecover.org), as well as the CSIC project (PIEC 200430E599). Support of this work was also provided by the Agency for Management of University and Research Grants (to NT, research contract Beatriu de Pinós 2009-BP-263), the Spanish Ministry of Science and Innovation (to E. Casas, doctoral fellowship linked to Biorock project CTM2009-08045; to CL, research contract Ramo´n y Cajal), and the Spanish National Research Council (to E. Cebrián, research contract JAE doc)

El delta de l’Ebre presenta les característiques idònies per ser un gran laboratori a l’aire lliure per a l’observació de llamps i d’altres fenòmens elèctrics, que tenen lloc per sobre dels núvols de tempesta. Aquests cosins dels llamps, de formes sorprenents, no es van descobrir fins a finals dels 90 i han despertat un gran interès en la comunitat científica.

Com a conseqüència d'una remodelació de rasants dels carrers propers, s'han detectat problemes ocasionats per l'acumulació d'aigües pluvials a la cruïlla entre els carrers Marinada i Sant Sebastià del nucli urbà de Sant Pere Pescador. Es planteja eliminar les inundacions locals mitjançant una actuació a la xarxa. Es preveu en primera instancia el disseny, la descripció i la valoració de les obres necessàries per desguassar les aigües pluvials acumulades mitjançant un dipòsit de regulació d'aigües pluvials i un bombament.

In lightning protection techniques a basic aspect is the identification of the impact point possible, which is determined by the evolution of the initial phase of the lightning, known as the stepped leader, the ground geometry and structures on it. In general, the available theoretical models are consistent with ideal situations and do not include situations such as non-vertical trajectories, non-flat terrain or complex structures. This work reviews and compares the most outstanding models in the literature on this subject and proposes a model for the study of the stepped leader based on the Finite Element Method (FEM). With the intention of bringing the process to the real situation of progress of a downward negative leader, who can follow a trajectory 3D, several modeling aspects are contemplated, as: adjusting the charge density in the channel, the length and direction of jump, which can be modified depending on the height that is the leader, and the propagation delays caused by the distance from the observation point. On the other hand, the model allows the implementation of 3D geometries and the incorporation of complex structures and non-flat terrain, providing results in situations when it is not possible to have theoretical approaches. Simulations have been performed with different proposals for charge distribution in the channel, in situations of leader vertical, inclined and 3D trajectory. The model has been evaluated, comparing their results with theoretical ideal cases and reproducing some real situations from field measurements. The application of the model in simulating real cases for downward negative leader provides parameter values that are not available through the recorded measurements and are useful for studying this type of discharge. In this work we have focused on some of them, and we have obtained interesting results as: estimating the speed of the leader according of height (from the measures of ¿E (t)), the definition of new relationships between charge density in the channel, ¿Emax (leader close to ground), the return peak current and the observation point distance, as well as we can verify the conditions of inception for a discharge into a storm cloud. Finally, we use the model to evaluate the striking distance, a basic concept on protection techniques. It is inferred a new equation for its calculus and the results are compared with proposals available in the literature, showing good agreement with the recommendation of IEC 62305-1. The results encourage to continue the study and they open the possibility to extend the method to other stages, not only on the downward leader, but also on other phenomena related to the formation and evolution of storm situations., En las técnicas de protección contra el rayo un aspecto básico es la identificación del posible punto de impacto, que viene determinado por la evolución de la fase inicial de la descarga atmosférica, conocida como líder escalonado (stepped leader), y por la geometría del terreno y estructuras sobre él. En general, los modelos teóricos disponibles se ajustan a situaciones ideales y no contemplan situaciones como trayectorias no verticales, terreno no plano o estructuras complejas. En este trabajo se revisan y comparan los modelos más destacados en la bibliografía sobre el tema y se propone un modelo para el estudio del stepped leader basado en el Método de los Elementos Finitos (FEM). Con la intención de aproximar el proceso a la situación real de avance de un líder negativo descendente, que puede seguir una trayectoria 3D, en el modelado se contemplan aspectos como: el ajuste de la densidad de carga en el canal, la longitud y dirección del salto, que pueden ser modificadas en función de la altura a la que se encuentre el líder, y los retardos de propagación provocados por la distancia del punto de observación. Por otra parte, el modelo permite la implementación de geometrías en 3D y la incorporación de estructuras complejas y terreno no plano, facilitando obtener resultados en situaciones en las que no es posible disponer de aproximaciones teóricas. Se han realizado simulaciones con diferentes propuestas de distribución de carga en el canal y para situaciones de líder vertical, inclinado y con trayectoria 3D. El modelo ha sido evaluado, contrastando sus resultados con casos teóricos ideales y reproduciendo situaciones reales a partir de diversas medidas de campo. La aplicación del modelo en la simulación de casos reales para líder negativo descendente nos proporciona valores de parámetros que no están disponibles a través de las medidas registradas y que son de utilidad para el estudio de las descargas negativas descendentes. En este trabajo nos hemos centrado en algunos de ellos y se han obtenido resultados de interés como: una estimación de la velocidad de avance del líder en función de la altura (a partir de medidas disponibles de ΔE(t)), la definición de nuevas relaciones entre densidad de carga en el canal, ΔEmax (líder próximo a tierra), la corriente de pico de retorno y la distancia del punto de observación, además de verificar las condiciones de inicio de descargas en una nube de tormenta. Por último, se utiliza el modelo para la evaluación de la distancia de cebado (striking distance), concepto básico en técnicas de protección. Se infiere una nueva ecuación para su cálculo y se comparan los resultados con las propuestas disponibles en la literatura, mostrando una buena concordancia con la recomendación de la norma IEC 62305-1. Los resultados obtenidos animan a continuar con el estudio y abren la posibilidad de ampliar la aplicación del método a otras etapas, no sólo en la descarga descendente, sino también de otros fenómenos relacionados con la formación y evolución de las situaciones de tormenta., En les tècniques de protecció contra el llamp, un aspecte bàsic és la identificació del possible punt d’impacte, que ve determinat per l’evolució de la fase inicial de la descàrrega atmosfèrica, coneguda com a líder esglaonat (stepped leader), i per la geometria del terreny i les estructures que hi ha a sobre d’ell. En general, els models teòrics dsiponibles s’ajusten a situacions ideals i no contemplen situacions com trajectòries no verticals, terreny no pla o estructures complexes. En aquest treball es revisen i comparen els models més destacats en la bibliografia sobre el tema i es proposa un model per a l’estudi del stepped leader basat en el Mètode dels Elements Finits (FEM). Amb la intenció d’apropar el procés a la situació real d’avançament d’un líder negatiu descendent, el qual pot seguir una trajetòria 3D, en el modelat es contemplemn aspectes com: l’ajustament de la densitat de càrrega al canal, la longitud i la direcció del salt, que poden ser modificades en funció a l’altura on es trobi el líder i als retards de propagació provocats per la distància del punt d’observació. D’una altra banda, el model permet la implementació de geometries en 3D i la incorporació d’estructures complexes i terreny no pla, facilitant així l’obtenció de resultats en situacions on no es possible disposar d’aproximacions teòriques. S’han realitzat simulacions amb diferents propostes de distribució de càrrega al canal i per a situacions de líder vertical, inclinat i amb trajectòria 3D. El model ha estat avaluat, contrastant els seus resultats amb casos teòrics ideals i reproduint situacions reals a partir de diferents mesures de camp. L’aplicació del model en la simulació de casos reals per a líder negatiu descendent ens proporciona valors de paràmetres que no estan disponibles a travès de les mesures registrades i que són d’utilitat per a l’estudi de les descàrregues negatives descendents. En aquest treball ens n’hem centrat en alguns i s’han obtingut resultats d’interès com: una estimació de la velocitat d’avançament del líder en funció d’altura (només a partir de mesures disponibles de ΔE(t)), la definició de les noves relacions entre densitat de càrrega al canal, ΔEmax (líder proper a terra), el corrent del pic de retorn i la distància del punt d’observació, a més de verificar les condicions d’inici de descàrregues en un núvol de tempesta. Per últim, s’utilitza el model per a l’avaluació de la distància de d'encebament (striking distance), concepte bàsic en tècniques de protecció. S’infereix una nova equació per al seu càlcul i es comparen els resultats amb les propostes disponibles en la literatura, mostrant una bona concordància amb la recomanació de la norma IEC 62305-1. Els resultats obtinguts animen a continuar amb l’estudi i obren la posibilitat d’ampliar l’aplicació del mètode a d’altres etapes, no només en la descàrrega descendent, sinó també d’altres fenòmens relacionats amb la formació i evolució de les situacions de tempesta.

Junta Comunidades Castilla- La Mancha, Ministerio de Ciencia e Innovación, Ministerio de Educación y Ciencia, European Commission

Real coastal waves measured at 4 different locations in the world were analyzed in detail. Long travelled swell measured in the Pacific coast of Costa Rica, wind swell from the Atlantic coast of Costa Rica, short period wind waves from the Ebro Delta in Mediterranean coast of Spain, and waves measured during the passing of Hurricane Wilma near Cancun, Mexico were analyzed. A total of 5795 wave records from the sites above were analyzed. A statistical stability analysis of the wave data was done. The measured wave height distribution was compared with the Raleigh distribution. The corresponding significant wave height and period distribution based on the zero down crossing method was obtained for all the records. The joint individual wave height-period distribution was obtained and the characteristic statistic wave heights and periods were obtained. The time variation of these parameters, including the skewness and kurtosis of the time series were obtained to determine the statistical stability of the data. A detailed spectral analysis using the Fourier transform was done on all the records. The whole record for each location was represented as time variant frequency energy spectrogram. The highest measured record’s spectra for each site were examined in detail. The peakedness, band width, grouping, regularity spectral parameters, and the six principal moments of all the wave records were obtained. The spectra were then compared to the JONSWAP spectrum. Special attention was taken into the non-linear components present in the spectra. Temporal and energetic wave grouping parameters were analyzed using the run length theory. Low frequency modulation was examined against grouping observation. The capability of the variance spectra based on the Fourier transform to describe the measured wave grouping was analyzed and confirmed through the spectral grouping parameter Ka. The long waves present in the records were analyzed using a low pass filter. Spectral analysis was carried out on the filtered time series. The results between the different sites were compared and Longuet-Higgins set down equation under wave groups was calibrated and validated to predict the long wave spectral significant wave height, given the wave spectral significant height, the peak spectral period and the water depth outside the breaker zone. A spectral analysis using the Hilbert Huang method was done to the most energetic measured events of each record. A detail comparison was done between the result of the Fourier transform variance spectral analysis and the Hilbert Huang method. The limitations of the Fourier based spectra and the new Hilbert Huang transform spectra were examined in detail.

Sprites and Elves are commonly observed in Europe, especially also in winter maritime storms. It is well known that sprites are related to large electric charge positive flashes and elves are related with high amplitude in either negative and positive flashes. The analysis of the occurrence of sprites and elves revealed that sprites can occur inland and over the sea whereas elves prefer to occur over the sea. The distribution of positive and negative flashes during the warm period (April-September) and the cold period (October-March) depicts that flashes with intense amplitudes present a particular pattern. Intense negative flashes occur mostly over the sea and coastal areas during summer and winter whereas intense positive tend to occur in the mountains during the warm season and over sea during the cold period. Also, sprite and elves can indicate regions where energetic flashes occur. This can be a valuable information related to the risk assesment of wind turbines.